Izuna Uchiha is Madara Uchiha's younger brother. He was alive about 70 years before the start of the series, even before the founding of Konoha. Standing at the top of the Uchiha clan with his brother, Izuna was one of the first to obtain the elusive "Mangekyou Sharingan" (along with Madara). However, Madara went blind due to the use of his. To alleviate this, Izuna gave up his eyes so that Madara would obtain a new, "permanent" Mangekyou.